The energy loss of heavy quark in the plasma has been of great
interest in recent times. The energy loss mechanisms of heavy quarks
are different from that of light quarks: gluon radiation is suppressed
[1]} in a cone of angle \(\tfrac{m_{\scriptscriptstyle Q}}{E}\) . For quarks of moderate
energy, collision with thermal particles is the
leading energy loss mechanism [2]}. Since even for a
near-thermalized heavy
quark, its momentum \(p_{\scriptscriptstyle Q}\sim \sqrt{m_{\scriptscriptstyle Q}T} \gg T\) , individual
collisions with light thermal particles with momentum \(\sim T\)  do not
change the momentum of a heavy quark significantly. Therefore, a
Langevin description of the heavy quark energy loss for
low-intermediate energy heavy quarks was proposed:
[3]}, [2]}, [5]}
\(\frac{dp_i}{dt} \; = \; - \eta \, p_i \; + \; \xi _i(t), \qquad \langle \xi _i(t) \, \xi _j(t^\prime ) \rangle \; = \; \kappa \;\delta _{ij} \; \delta (t-t^\prime )\) 
